1. Field of the Invention
The present invention relates to a mobile communication system, an access router, a management device, and a mobile communication method.
2. Description of the Related Art
Recently, a mobile communication system using a user address retained by a communication terminal and a routing address assigned on a network besides the user address in order to transfer a packet has been under discussion (see, for example, Japanese Patent Application Laid-Open No 2004-112727 and Takatoshi okagawa, et. al., “IP Packet Routing Mechanism Based on Mobility Management in IP-based IMT Network Platform”, 8th International Conference on Intelligence in next generation Networks, April 2003, hereinafter, referred to as a “document 1”).
Hereinafter, the mobile communication system using a user address and a routing address is referred to as a “core-network proxy network system”. Further, the core-network proxy network system has been proposed in which a border router provided at the boundary with an external network assigns a routing address to a mobile terminal that has transmitted a packet and exists in the external network when receiving the packet from the mobile terminal (see, for example, Katsutoshi Nishida, Takatoshi Okagawa, “A Proposal for Interconnecting IP 2 and Exiting IP Networks”, The Society Conference of the Institute of Electronics, Information and Communication, September 2003, hereinafter, referred to as a “document 2”).
On the other hand, the mobile IP has been proposed as a technique for ensuring mobility in a mobile communication system (see, for example, “Mobility Support in IPv6”, draft-ietf-mobileip-ipv6-24.txt, June, 2003). Specifically, an MIP terminal (Mobile IP terminal) equipped with a mobile IP technique uses a home address (hereinafter, referred to as a “HoA”) assigned in a home link, and a care of address (hereinafter, referred to as a “CoA”) acquired on in an external link. Then, a home agent (hereinafter, referred to as an “HA”) arranged in the home link manages the HoA and the CoA and transfers a packet to the MIP terminal even if the MIP terminal has moved to the external link